This invention relates to certain aromatic polyesteramides which exhibit desirable melt processability and hhich are useful in the production of films and fibers. More particularly, it relates to aromatic polyesteramides containing para-linked, substituted-phenylene radicals interconnected by ester and amide linkages. The polyesteramides exhibit melt anisotropy at temperatures of approximately 260.degree. C. and lower, and preferably, below approximately 240.degree. C.
The production of polyamides, polyesters and polyesteramides suitable for high strength service without the use of reinforcing agents has been well known. These polymers have been variously described as being "liquid crystalline", "thermotropic", "mesogenic", and "anisotropic". In general, these polymers are thought to be characterized by parallel ordering of their molecular chains and are prepared from monomers which are generally long, flat and fairly rigid along the long axis of the molecule. The monomers commonly have chain-extending linkages that are coaxial or parallel. Numerous patents and publications describing polyesters, polyamides and polyesteramides are cited, for example, in U.S. Pat. No. 4,351,918, issued Sept. 28, 1982 to L. F. Charbonneau, et al.
In general, it is well recognized that the mechanical and physical properties of polymeric films and fibers will depend upon the chemical structure of the monomers from which they are prepared and that such properties can be materially influenced by such molecular factors as chain stiffness, intermolecular forces, orientation and crystallinity. Accordingly, there has been considerable interest in the development of polyesters, polyamides and polyesteramides, having particular structural or molecular configurations for the realization of one or more particular properties suited to a desired application. Notably, there has been particular interest in the development of melt processable polymers capable of forming an anisotropic melt phase and suited to processing into films and fibers.
In the production of melt-processed films and fibers from aromatic polyesters and polyesteramides, melt processability is frequently hampered by the tendency of such materials to be melt processable only at elevated temperatures which, in someiinstances, may approach the onset of thermal degradation. In U.S. Pat. No. 4,575,547 (issued Mar. 11, 1986 to H. G. Rogers, et al.), and in U.S. Pat. No. 4,608,429 issued Aug. 6, 1986 to H. G. Rogers, et al.), aromatic polyesters suited to melt processing into films and fibers are described. The polyesters of these patents are especially advantageous from the standpoint of their processability at lower temperatures, e.g,, in the range of about 115.degree. C. to 205.degree. C. The improved melt processability of these polyesters, relative to aromatic polyesters in general, which are only melt processable at higher temperatures, permits improved handling of the polymers and allows for the production of polymeric films and fibers. Frequently, however, it will be advantageous that a polymeric material exhibit a desirable balance of mechanical properties suitable for high strength service, while still being adapted to processing into films and fibers by resort to general molding and melt processing methods and without need for the use of solvent materials and the handling and recovery operations associated therewith. Moreover, it will be advantageous where a combination of high strength properties and practical melt processability can be realized in a polymer containing repeating units derived from a minimal number of reactants.